Preparation of 2,2&#39;,4,4&#39;,6,6&#39;-hexanitrodiphenylamine



Dec. 24, 1968 F. TmiLoR, JR

PREPARATION OF 2 2, 4 4, 6 6 HEXANITRODIPHENYLAMINE Filed Jan. 29. 1960 INVEN TOR. FRANCIS TAYLOR JR. Q W

ATTY s.

United States Patent 3,418,372 PREPARATION OF 2,2,4,4,6,6-HEXA- NITRODIPHENYLAMINE Francis Taylor, Jr., Catonsville, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Jan. 29, 1960, Ser. No. 5,574 1 Claim. (Cl. 260-576) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This application relates generally to the ordnance art and is more particularly concerned with the preparation of a potassium salt of hexanitrodiphenylamine and a process employing this material as a high temperature booster explosive.

Many of the booster explosives currently in military use have been employed with but indifferent success in missiles. One of the reasons for this is that many of these explosives are unstable at elevated temperatures and decompose when subjected to high temperatures for prolonged periods. The aerodynamic heating effects encountered during the passage of a high speed missile warhead through the earths atmosphere causes the present day booster explosives to :boil off thereby disarming the weapon. Those explosives which are stable enough to withstand the elevated temperatures encountered have been found to possess certain inherent deficiencies which make them unsuitable for use as booster explosives when employed with high speed missile. For example the detonation velocity of certain materials is too low, while the heat of explosion of others was found to be unsatisfactory.

It is an object of the present invention to provide an improved method of boostering an explosive warhead at temperatures in excess of 100 C.

Another object of this invention is to provide an improved composition of matter useful as a booster explosive.

Still another object of the invention is the provision of a novel process for the preparation of ultra pure potassium hexanitrodiphenylamine.

These and many other objects will become more readily apparent when the following specification is read and considered along with the attendant drawing which represents a missile employing a booster made according to the principles of this invention.

Melting point, O

Impact sensitivity, cm Vacuum stability:

Cc. gas/gJ48 hrs. at 100 C Cc. gas/gJhr. at 260 C Crystal 1 1% decomposition.

Composition density Detonation Velocity, meters/sec Hexanitrodiphenylamine (C12H5N7O12) is known in the chemical art. By treating hexanitrodiphenylamine (HND) with potassium acetate in ethyl alcohol the potassium salt of HND (KHND) is formed. This reaction of the HND has been used in the gravimetric determination of potassium. The relatively impure KHNlD prepared in this manner is unsuitable for use as a booster explosive because it is unstable at elevated temperatures.

It has been found that if HND is reacted with potassium acetate in acetone the KHND produced is 99.7 mole percent pure. Apparently the physical properties of pure KHND are much improved over those of KHND prepared by slurrying the free acid (HND) in alcohol and reacting it with potassium acetate. The reason is that when an alcohol slurry of HND is reacted with potassium acetate, the conversion of HND to KHND is about 93%. The product, KHND, therefore contains HND as an impurity which cannot easily be separated from the KHND because of the similar properties of HND and KHND. HND is a liquid at temperatures about 244 C. and decomposes rapidly at higher temperatures. Accordingly, KHND produced according to the prior art processes is more unstable at higher temperatures due to the decomposition of the HND impurity. The following example is given by way of illustration:

Example 1 Ten grams of HND is suspended in 100 milliliters of acetone. To this was added 22.4 grams of potassium acetate dissolved in 100 milliliters of alcohol and ml. of acetone. Upon the addition of potassium acetate, the suspension of HND dissolved completely. The reaction mixture was stirred for thirty minutes at room temperature and then diluted with water until it became turbid. This turbid product was chilled, the KHND precipitated, the salt collected on a Buchner funnel, washed with cold water and dried. The crude product was 99.7 mole percent pure and it did not require recrystallization before use. The equivalent weight of the product of Example 1 was found to be 477 and the melting point was above 400 C. The material exhibited a crystal density of 1.85.

Table 1 is a comparison of KHND made according to the prior art processes, KHND made according to the instant process, and two typical booster explosives now in usetetryl (2,4,6-trinitrophenylmethylnitramine) and HMX (cyclotetramcthylenetetranitramine).

TAB LE 1 Prior Art Tetryl 2 93% crystal density.

Vacuum stability is a standard test used to measure the stability of an explosive; the amount of gas which evolves from the material at the stated temperature is an indication of the materials stability at that temperature. The greater the rate of gas evolution, the less stable is the composition. Conventional booster explosives are generally tested for vacuum stability at 100 C. However the test at this temperature is an insufficient indication of the stability of the more stable materials. Furthermore, it is not a realistic test of the stability of the material to be used at a temperaure Wthich is likely to exceed 100 C. For this reason, stability at 260 C. is a more realistic test for this purpose. As shown in the table the stability of KHND (pure) is much greater at 100 C. and 260 C. than that of tetryl, HMX or KHND prepared according to the process of the prior art. The melting point of HMX is rather high but it was found that it decomposes rapidly at two or three hundred degrees C.

Although HMX and tetryl both have greater detonation velocities these velocities cannot be realized at high temperatures. Thus, the advantage of tetryl and HMX over KHND (pure) in this respect is more apparent than real.

The impact sensitivity of KHND is comparable to that of HMX and is satisfactory for use as a booster. The impact sensitivity was measured by the standard test in which a 2.5 kilogram weight was dropped upon a sample of the explosive being tested. The height from which the weight caused the material to detonate 50% of the time is recorded as an indication of the sensitivity. The greater the height from which the weight must be dropped to detonate the material, the less sensitive the material is.

The thermal stability of pure KHND was further compared with HMX by a cook off test in which a half inch by one-half inch cylinder of the explosive was encased in copper and exposed to a rapid air stream at 310 C. The HMX cooked otf in 7.8 minutes while the KHND prepared according to this process required 19.5 minutes to cook off. It should be apparent to those skilled in the art that booster explosive composed of KHND made according to this process may be used at temperatures higher than those to which HMX, tetryl or other known booster explosive may be judiciously subjected.

Small scale detonation velocity measurements of KHND (pure) made at 93% of voidless density indicated a detonation velocity of 6900 meters per second. The output of KHND as determined by the plate dent technique showed it to be approximately equal to TNT at the same percentage of voidless density.

Referring now to FIG. 1 which shows a typical application of KHND booster a missile 11 contains an explosive charge 12 which may be RDX, TNT or any other conventional high explosive. As missile 11 moves through the atmosphere, aerodynamic heating raises the inside temperature several hundred degrees. The booster cup 13 contains KHND as shown at 14. A primer charge 15 is inserted into the booster and is detonated by generation of a firing signal by the fuze 16. Upon the generation of a firing signal the primer, which may be lead azide, is initiated to detonate the booster charge which in turn detonates the main explosive charge 12. As stated hereinbefore, the detonation velocity of KHND is about 7000 meters per second which is sufficiently high to detonate explosives conventionally employed. It should be obvious to those skilled in the art that by preparing KHND in ultra pure form it is possible to provide a booster which is reliable at high temperatures.

Having thus described this invention with reference to but a single embodiment, it is to be understood that it is by no means so limited but is susceptible of many alterations and modifications without departing from the spirit and scope thereof. Accordingly this invention is not to be construed as limited by the foregoing illustrative examples but is to be defined only by the scope of the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. The method of preparing 2,2',4,4' hexanitrodiphenylamine of a purity at least 99.7 mole percent which comprises the steps of mixing hexanitrodiphenylamine with acetone to form a slurry, dissolving potassium acetate in about a two to one mixture of alcohol and acetone to form a first solution, adding the first solution to the suspension, to form a second solution, adding sufiicient water to the second solution to cause the mixture to become turbid, chilling the mixture, and recovering potassium 2,2,4,4, 6,6-hexanitrodiphenylamine as a precipitate.

References Cited UNITED STATES PATENTS 2,595,568 5/1952 Dijkema et al. 260576 XR 1,948,330 2/1934 Calvert 260576 2,783,278 2/1957 Thelin et al. 260576 2,881,703 4/1959 Volpert 10286.5 2,872,870 2/1959 Gey 10286.5

OTHER REFERENCES Wintershall, Ger. 1,003,221, C.A., vol 53, 1959, p. 193250.

CHARLES B. PARKER, Primary Examiner.

P. C. IVES, Assistant Examiner.

US. Cl. X.R. 

1. THE METHOD OF PREPARING 2,2'',4,4'' - HEXANITRODIPHENYLAMINE OF A PURITY AT LEAST 99.7 MOLE PERCENT WHICH COMPRISES THE STEPS OF MIXING HEXANITRODIPHENYLAMINE WITH ACETONE TO FORM A SLURRY, DISSOLVING POTASSIUM ACETATE IN ABOUT A TWO TO ONE MIXTURE OF ALCOHOL AND ACETONE TO FORM A FIRST SOLUTION, ADDING THE FIRST SOLUTION TO THE SUSPENSION, TO FORM A SECOND SOLUTION, ADDING SUFFICIENT WATER TO THE SECOND SOLUTION TO CAUSE THE MIXTURE TO BECOME TURBID, CHILLING THE MIXTURE, AND RECOVERING POTASSIUM 2,2'',4,4'', 6,6''-HEXANITRODIPHENYLAMINE AS A PREDIPITATE. 